Additively manufactured impeller

ABSTRACT

An impeller including a blade section, a shroud section, and a hub is made of a monolithic structure. The impeller is made by loading a 3D image file into an additive manufacturing device, using it to generate 2D files which correspond to a plurality of cross-sectional layers of the impeller, and solidifying corresponding portions of pulverant material layers to create the impeller.

BACKGROUND

This invention relates generally to the field of additive manufacturing.In particular, the present invention relates to articles made byadditive manufacturing.

Additive manufacturing refers to a category of manufacturing methodscharacterized by the fact that the finished part is created by layerwiseconstruction of a plurality of thin sheets of material. Additivemanufacturing may involve applying liquid or powder material to aworkstage, then doing some combination of sintering, curing, melting,and/or cutting to create a layer. The process is repeated up to severalthousand times to construct the desired finished component or article.

Various types of additive manufacturing are known. For example,stereolithography (additively manufacturing objects from layers of acured photosensitive liquid), Electron Beam Melting (using a pulverantmaterial as feedstock and selectively melting the pulverant materialusing an electron beam), Laser Additive Manufacturing (using a pulverantmaterial as a feedstock and selectively melting the pulverant materialusing a laser), and Laser Object Manufacturing (applying thin, solidsheets of material over a workstage and using a laser to cut awayunwanted portions) are known.

Impellers are used in a variety of applications. Impellers are objectswhich redirect axial fluid flow into radial fluid flow. Impellers havetraditionally been made in two portions: a hub with blades and/orairfoils which redirect the airflow; and a shroud which circumscribesthe hub. These two portions are typically brazed to one another to formthe finished impeller. The hub and shroud portions have traditionallybeen manufactured separately, then combined by brazing. Brazing oftenresults in hazardous conditions during manufacturing, due to use ofmaterials of concern, such as carcinogens.

SUMMARY

An impeller includes a hub, blades, and a shroud, and is made from amonolithic material. An impeller may be made of a monolithic structureby generating a 3D image file corresponding to the desired impeller, andusing it to generate a plurality of 2D image files. An additivemanufacturing apparatus uses the 2D files to generate a correspondingseries of sintered layers of pulverant material to form the impeller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an additive manufacturing apparatuswhich may be used to generate an impeller.

FIG. 2 is a perspective view of an impeller made by additivemanufacturing.

FIG. 3A is a cross-sectional view of a prior-art impeller.

FIG. 3B is a cross-sectional view of the impeller of FIG. 2.

FIG. 4 is a cross-sectional view of the impeller of FIG. 2 taken alongline 4-4.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of an additive manufacturing apparatus. Inparticular, FIG. 1 shows a direct metal laser sintering apparatus.Additive manufacturing system 10 includes radiation source 12, radiationbeam 14, mirror 16, movable optical head 18, frame 20, pulverantmaterial supply 22, pulverant material bed 24, sintered pulverantmaterial 26, and spreader 28. Additive manufacturing system 10 may beused to create additively manufactured components, such as impellers.Many alternative designs of additive manufacturing devices are possible.Various additive manufacturing devices are commercially available. Thesedevices perform additive manufacturing through processes known asselective laser sintering, direct metal laser sintering,stereolithography, laser-engineered net shaping, laminated objectmanufacturing, e-beam melting, and laser powder deposition, amongothers. FIG. 1 merely illustrates one potential additive manufacturingsystem for creating an additively manufactured impeller 40 (FIG. 2).

Radiation source 12 may be any source capable of creating focusedradiation. For example, radiation source 12 may be a laser or anelectron beam. Radiation beam 14 is a beam of focused or focusableradiation, such as a laser beam or an electron beam. Minor 16 is presentin some embodiments to deflect radiation in a desired direction. Movableoptical head 18 is present in some embodiments, and also deflectsradiation in a desired direction. For example, movable optical head 18may include a minor and be attached to an x-y positioning device. Frame20 is used to contain pulverant material, in pulverant material supply22 and in pulverant material bed 24. Pulverant material supply 22 andpulverant material bed 24 include pulverant material, such as granularor powdered metals, ceramics, or polymers. Pulverant material bed 24further includes sintered pulverant material 26. Sintered pulverantmaterial 26 is pulverant material contained within pulverant materialbed 24 which has been at least partially sintered or melted. Spreader 28is a spreading device which may transfer pulverant material frompulverant material supply 22 to pulverant material bed 24.

Radiation source 12 creates radiation beam 14 which can be used formelting, sintering, or cutting. Radiation source 12 is pointed towardsmirror 16, which is arranged to deflect incident radiation toward movingoptical head 18. Generally, radiation beam 14 will be targeted withinframe 20, which holds pulverant material in pulverant material supply 22and pulverant material bed 24. At least some of the pulverant materialin pulverant material bed 24 is at least partially sintered or melted toform sintered pulverant material 26. Spreader 28 is positioned alongframe 20 in order to move pulverant material between pulverant materialsupply 22 and pulverant material bed 24.

Radiation source 12 generates radiation beam 14. Radiation beam 14travels to minor 16, and is redirected by minor 16 towards movingoptical head 18. Moving optical head directs radiation beam 14 towardsareas within pulverant material bed 24 in frame 20, which are melted orsintered. Sintered pulverant material 26 includes a layer of a desiredadditively manufactured component. Voids may be created in the desiredcomponent by not sintering or melting those portions of sinteredpulverant material 26. After each layer of the desired additivelymanufactured component is finished, a support (not shown) lowers theheight of pulverant material bed 24 with respect to frame 20. Likewise,a support (not shown) raises the height of pulverant material supply 22with respect to frame. Spreader 28 transfers a layer of pulverantmaterial from pulverant material supply 22 to pulverant material bed 24.

By repeating the process several times, a layer-by-layer object, such asimpeller (FIGS. 2-4, 40) may be manufactured. Components manufactured inthis manner may be made as a single, solid component, without brazejoints, welds, or undesirable weaknesses created during traditionalmanufacturing.

FIG. 2 is a perspective view of impeller 40. Impeller 40 includes shaft42, inlet 44, shroud 46, and outlets 48. Impeller 40 is used to directairflow from an axial direction to a radial direction. For example,impeller 40 may be used in aerospace application to create shorter gasturbine engines by replacing an axial compressor, or to providepressurized air for auxiliary airplane functions. Shaft 40 is an objectused to rotate impeller 40. As shown in FIG. 2, shaft 42 is a hollow barwith a primary length in the axial direction of impeller 40. Inlet 44includes an aperture in impeller 40. Typically, inlet 44 is attachableto an adjacent component which generates or allows axial airflow towardsimpeller 40. For example, inlet 44 may include a grommet connected toimpeller 40 and sealed to a plenum. Shroud 46 is an outer housing ofimpeller 40, which contains internal components such as internalpassages 50 (FIG. 3) and impeller blades 52 (FIG. 3). Outlets 48 arearranged at a radially outward portion of impeller 40. Typically,outlets 48 generate pressurized air streams directed radially outwardfrom impeller 40.

As shown in FIG. 2, shaft 42, inlet 44, shroud 46, and outlets 48 are asingle, monolithic component. As shaft 42 is rotated, the rest ofimpeller 40 also rotates. Rotation of impeller 40 generates fluid toflow towards outlets 48 from inlet 44. Impeller 40 has been additivelymanufactured from a single material. The material may be any suitablematerial for an impeller, such as titanium, aluminum, orhigh-temperature superalloys. Many of the materials which may beadditively manufactured to form impeller 40, such as titanium, aluminum,and some high-temperature superalloys, are unsuitable for brazing.Because of their stable surface oxides, these materials often cannot bebrazed without applications of high levels of heat and/or surroundingthe material with a reducing atmosphere during brazing. Thus, impeller40 presents improvements in strength, weight, and/or durability overimpellers made using traditional manufacturing.

FIG. 3A is a cross-sectional view of prior-art impeller 140. FIG. 3Ashows similar parts to those described with respect to FIG. 2. Forexample, prior-art impeller 140 includes shaft 142, inlet 144, andshroud 146. In addition, FIG. 3A shows the interior structure ofprior-art impeller 140, including internal passages 150, and impellerblades 152 attached to hub 154. Further, prior-art impeller 140 includesbraze joint 156.

Braze joint 156 must be sufficiently strong to hold impeller blades 152to shroud 146 during rapid rotation of prior-art impeller 140. Thus,only materials with good brazing characteristics, such as weak surfaceoxides, have been used for prior art impellers 140. For example, variousgrades of steel are often used. These materials tend to be heavy, anddeteriorate more rapidly than other available non-brazable metals, suchas titanium- and aluminum-based alloys.

FIG. 3B is a cross-sectional view of impeller 40. FIG. 3B includes manyof the same parts as shown in FIG. 2, such as shaft 42, inlet 44, andshroud 46 of impeller 40. In addition, FIG. 3 shows internal passages50, impeller blades 52, and hub 54. Internal passages 50 provide aflowpath for fluid passing from input 44 to outlets 48 (FIG. 2).Internal passages 50 have borders defined by shroud 46 and impellerblades 52. Impeller blades 52 at least partially fill the interior ofshroud 46 and, during rotation, cause fluid to flow towards outlets 48(FIG. 2).

Fluid at inlet 44 passes through the interior of shroud 46 and iscontained within internal passages 50. As shaft 42 is rotated, the restof impeller 40 rotates as well. Impeller blades 52 push fluid withinimpeller 40 radially outward. This causes pressure to drop at inlet 44,and causes pressure to rise at outlets (FIG. 2, 48). Hub 54 preventsfluid from continuing to flow in axially. Thus, fluid is expelledthrough outlets (FIG. 2, 48).

Notably, impeller 44 does not include a braze joint. Impeller 44 made byadditive manufacturing may be made by any material so long as it iscapable of being used in an additive manufacturing process. Thus, thedrawbacks discussed with respect to prior-art impeller 144 (FIG. 3A) areobviated.

FIG. 4 is a cross-sectional view of impeller 40 taken along line 4-4 ofFIG. 2. FIG. 4 shows a possible design of impeller blades and internalpassages 50. FIG. 4 shows many of the same parts as described withrespect to FIGS. 2 and 3B. In particular, FIG. 4 shows impeller 40,internal passages 50, impeller blades 52, and hub 54. As described withrespect to FIGS. 2-3, impeller 40 is a monolithic component built usingadditive manufacturing. Thus, impeller blades 52 and hub 54 are made ofthe same piece of material as shaft 40 (FIGS. 2, 3B) and shroud 46(FIGS. 2, 3B). As impeller 40 rotates counterclockwise, impeller blades52 cause fluid within internal passages 50 to flow radially outwards,away from hub 54. Fluid flow is contained from moving axially by shroud46 (FIGS. 2, 3B).

Because impeller 40 is additively manufactured, at least two importantadvantages are realized. First, impellers made using traditionalmanufacturing could not be machined as a single piece. Thus, typically,the impeller would be made by machining the desired impeller blades,then machining the shroud, and combining the two pieces by brazing.Brazed impellers are inherently weaker and require additional steps andmaterials to create. Second, because the braze joint is eliminated,additively manufactured impellers may be created from materials whichare not easily brazed. Typically, materials with stable surface oxidesare difficult or impossible to braze. For example, brazing oftitanium-based and aluminum-based alloys is often impracticable. Thus,traditional impellers are typically made from iron-based alloys such assteel. Additively manufacturing impeller 40 of titanium rather thansteel, for example, is beneficial in that many titanium alloys arestronger and more lightweight than steels.

Listing of Potential Embodiments

In one embodiment, the invention includes an impeller with a bladesection including a plurality of blades, wherein the blade section has adiameter and the blades extend radially from a hub, and a shroud sectioncircumscribing the blade section, connected to the radially outermostportions of the plurality of blades. The blade section, the shroudsection, and the hub comprise a monolithic structure of a material. Thediameter of the shroud section may be less than 20 cm., and themonolithic structure may extend less than 12 cm. axially. The impellermay be made of a material with a stable surface oxide, such as atitanium-based or an aluminum-based alloy. The impeller may also includea shaft connected to the monolithic structure, or the shaft may be apart of the monolithic structure.

In another embodiment of the invention, a method for making an impellerincludes loading a 3D image file into an additive manufacturing device,generating 2D files from the 3D image file which correspond to aplurality of cross-sectional layers of the impeller, and solidifying aportion of a pulverant material layer corresponding to each of theplurality of cross-sectional layers in a layerwise fashion to create theimpeller. The method may include using a material that has a stablesurface oxide, such as a titanium-based or an aluminum-based alloy. Themethod may include solidifying the pulverant material by lasing, or byfocusing an electron beam on the pulverant material. Solidifying thepulverant material may include at least partially melting the pulverantmaterial, or sintering the pulverant material. The method may alsoinclude removing the unsintered portions of the pulverant materiallayers. The impeller formed by this method may include a shroud and aplurality of blades, and those parts may be made of a monolithicstructure.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. An impeller comprising: a blade section including a plurality ofblades, wherein the blade section has a diameter and the blades extendradially from a hub; and a shroud section circumscribing the bladesection, connected to the radially outermost portions of the pluralityof blades, wherein the blade section, the shroud section, and the hubcomprise a monolithic structure of a material.
 2. The impeller of claim1, wherein the diameter of the shroud section is less than 20 cm.
 3. Theimpeller of claim 1, wherein the monolithic structure extends less than12 cm. axially.
 4. The impeller of claim 1, wherein the material has astable surface oxide.
 5. The impeller of claim 4, wherein the materialis a titanium-based alloy.
 6. The impeller of claim 1, furthercomprising a shaft connected to the monolithic structure.
 7. Theimpeller of claim 6, wherein the monolithic structure includes theshaft.
 8. A method of making an impeller, the method comprising: loadinga 3D image file into an additive manufacturing device; generating 2Dfiles from the 3D image file which correspond to a plurality ofcross-sectional layers of the impeller; and solidifying a portion of apulverant material layer corresponding to each of the plurality ofcross-sectional layers in a layerwise fashion to create the impeller. 9.The method of claim 8, wherein the pulverant material layer comprises amaterial having a stable surface oxide.
 10. The method of claim 9,wherein the material having a stable surface oxide is a titanium-basedalloy.
 11. The method of claim 8, wherein solidifying the pulverantmaterial layer includes lasing the pulverant material.
 12. The method ofclaim 8, wherein solidifying the pulverant material layer comprisesfocusing an electron beam on the pulverant material.
 13. The method ofclaim 8, wherein solidifying the pulverant material layer includes atleast partially melting the pulverant material.
 14. The method of claim8, wherein solidifying the pulverant material layer includes sinteringthe pulverant material.
 15. The method of claim 8, and furthercomprising removing the unsintered portions of the pulverant materiallayers.
 16. The method of claim 8, wherein the impeller formed bysolidifying the layers of the pulverant material includes a shroud and aplurality of blades.
 17. The method of claim 16, wherein the shroud andthe plurality of blades are made of a monolithic structure.